1. Field of the Invention
This invention relates to an optical element and a compound display apparatus using the same.
Besides, this invention relates to an optical system suitable for an image pickup display apparatus or the like which is enhanced in the degree of freedom of layout by the use of an optical element which is thin (thin in the direction of the visual axis) and is easy in the display and image pickup at a wide angle of field and has a free curved surface.
Besides, this invention relates to a compound display apparatus which has an image pickup optical system for introducing light from the image information of the external world and forming an image on an image pickup element and a display optical system for observing therethrough the image information displayed on display means such as liquid crystal and which is generally downsized, and particularly is suitable for an apparatus called a head mounted display (HMD) or a spectacle type display.
2. Related Background Art
There have heretofore been proposed an apparatus in which a compact CCD camera is mounted on an HMD and image information obtained from the compact CCD camera is intactly displayed on the HMD, and an apparatus in which image information obtained from a compact CCD camera is processed and converted into discrete image information, which is then displayed on an HMD. Also, there have been proposed various see-through type HMD""s (HMD""s designed such that the light of the external world can be directly observed at an angular magnification of about 1).
In the HMD""s of such a form, it is not preferable that when the eyeball optical axis of a display optical system for observing therethrough the image information displayed on the display means of the HMD and the optical axis of the CCD camera for imaging the image information of the external world on the surface of the CCD differ from each other, a parallax occurs between these. An apparatus having an image pickup optical system and a display optical system with no parallax each other is proposed in Japanese Patent Application Laid-Open No. 4-22358 and Japanese Patent Application Laid-Open No. 5-303053.
The display optical system proposed in Japanese Patent Application Laid-Open No. 4-22358 is such that light emitted from a compact LCD passes through a half mirror, and thereafter is imaged on a compact camera. On the other hand, the image pickup optical system is such that the light of the external world passes through a plane half mirror, and thereafter is imaged on the compact camera. This plane half mirror is disposed at 45xc2x0 with respect to the optical axis and therefore, the apparatus has tended to become bulky. Also, this apparatus has been of a construction in which eyepieces are in front of the eyeballs and therefore a see-through optical system is not realized.
Japanese Patent Application Laid-Open No. 5-303053 discloses a construction in which a see-through optical system is realized, but the optical system is complicated and the apparatus has tended to become very bulky.
HMD""s which have solved these problems are proposed in Japanese Patent Application Laid-Open No. 10-239628, Applicant""s Japanese Patent Application Laid-Open No. 11-174367, Japanese Patent Application Laid-Open No. 2000-75240, etc.
Each of the compound display apparatuses proposed in these publications uses two prism-shaped optical elements (free curved surface prism) having its so-called free curved surface having different power depending on the azimuth angle disposed appropriately in both of the display optical system and the image pickup optical system, and uses the joined surface of the both free curved surface prisms as optical path separating means such as a half mirror to thereby realize a compact compound display apparatus.
It is an object of the present invention to further improve the optical system proposed in the above-mentioned publications, and appropriately construct the free curved surface prisms (optical elements) of the display optical system and image pickup optical system and an imaging optical system to thereby provide an optical element which is compact and thin in the direction of the optical axis of the eyeball and suitable for a wider angle of field and a compound display apparatus using the same.
It is another object of the present invention to appropriately set the construction of a display optical system having a plurality of eccentric reflecting surfaces for directing a beam from display means such as a liquid crystal display (LCD) to an observer""s eyeball and the construction of an image pickup optical system for imaging the image information of the external world on the surface of an image pickup element such as a CCD to thereby provide a compound display apparatus which is generally downsized and yet enables the image information of the both optical systems to be observed and imaged in a good state.
It is still another object of the present invention to provide a compound display apparatus including a see-through optical system which also enables the image information of the external world to be observed at the same time.
To solve the above noted problems, the optical element of the present invention is an optical element having on the same medium an incidence surface, an emergence surface, and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of the plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, characterized in that the meridional section composite power of the optical element is negative.
In the above-described optical element, at least one of the plurality of eccentric reflecting surfaces may be a rotation-asymmetrical surface.
Also, in the above-described optical element, the emergence surface may be a rotation-asymmetrical surface.
Also, in the above-described optical element, all of the incidence surface, the emergence surface and the plurality of eccentric reflecting surface may be rotation-asymmetrical surfaces.
Also, in the above-described optical element, design may be made such that the local meridional section focal length fypout and local sagittal section focal length fxpout of the emergence surface and the meridional section composite focal length fyp and sagittal section composite focal length fxp of the optical element satisfy
|fyp/fypout| less than 2xe2x80x83xe2x80x83(1)
|fxp/fxpout| less than 2.xe2x80x83xe2x80x83(2)
Also, in the above-described optical element, the emergence surface may have negative power.
Also, to solve the above-noted problems, the optical element of the present invention is an optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of the plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, characterized in that at least one of the plurality of eccentric reflecting surfaces is a rotation-asymmetrical surface, and design is made such that the local meridional section focal length fypout and local sagittal section focal length fxpout of the emergence surface and the meridional section composite focal length fyp and sagittal section composite focal length fxp of the optical element satisfy
|fyp/fypout| less than 2xe2x80x83xe2x80x83(1xe2x80x2)
|fxp/fxpout| less than 2.xe2x80x83xe2x80x83(2xe2x80x2)
A compound lens unit may have at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, and all of the optical axis of the rotation-symmetrical surface of the rotation-asymmetrical lens and the optical axes of the rotation-symmetrical lenses may substantially coincide with one another.
Also, in the above-described compound lens unit, design may be made such that the local meridional section focal length fyl and local sagittal section focal length fxl of the rotation-asymmetrical surface and the meridional section composite focal length fyg and sagittal section composite focal length fxg of the compound lens unit satisfy
|fyg/fyl| less than 1xe2x80x83xe2x80x83(3)
|fxg/fxl| less than 1.xe2x80x83xe2x80x83(4)
Also, to solve the above-noted problems, an image pickup optical system of the present invention is an image pickup optical system which has a first optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of the plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, and the meridional section composite power is negative,
a stop, and
a compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, all of the optical axis of the rotation-symmetrical surface of the rotation-asymmetrical lens and the optical axes of the rotation-symmetrical lenses being substantially coincident with one another,
characterized in that design is made such that light from the external world is caused to be incident from the incidence surface, is reflected by the plurality of eccentric reflecting surfaces to thereby fold the optical path and is caused to emerge from the emergence surface, and is passed through the stop, and thereafter is refracted by the compound lens unit and is imaged on an image pickup element.
In the above-described image pickup optical system, design may be made such that when the meridional section composite focal length of the entire image pickup optical system is defined as fy and the sagittal section composite focal length thereof is defined as fx and the meridional section composite focal length of the first optical element is defined as fyp and the sagittal section composite focal length thereof is defined as fxp,
xe2x88x921 less than fy/fyp less than 0xe2x80x83xe2x80x83(5)
xe2x88x921 less than fx/fxp less than 0xe2x80x83xe2x80x83(6)
are satisfied.
Also, in the above-described image pickup optical system, deflecting means for bending the optical path in a direction differing from the direction in which the optical path of the first optical element is folded may be provided between the first optical element and the stop or between the stop and the compound lens unit.
Also, to solve the above-noted problems, in the image pickup optical system of the present invention, an image pickup optical system has a first optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of the plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, and at least one of the plurality of eccentric reflecting surfaces is a rotation-asymmetrical surface, and design is made such that the local meridional section focal length fypout and local sagittal section focal length fxpout of the emergence surface and meridional section composite focal length fyp and sagittal section composite focal length fxp of the first optical element satisfy the following conditional expressions:
|fyp/fypout| less than 2xe2x80x83xe2x80x83(1xe2x80x3)
|fxp/fxpout| less than 2xe2x80x83xe2x80x83(2xe2x80x3)
a stop, and
a compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, all of the optical axis of the rotation-symmetrical surface of the rotation-asymmetrical lens and the optical axes of the rotation-symmetrical lenses being substantially coincident with one another,
characterized in that design is made such that light from the external world is caused to be incident from the incidence surface of the first optical element and is reflected by the plurality of eccentric reflecting surfaces to thereby fold the optical path and is caused to emerge from the emergence surface, and is passed through the stop, and thereafter is refracted by the compound lens unit and is imaged on an image pickup element.
A compound display apparatus has the above-described image pickup optical system, an image pickup element, display means and a second optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a display reference ray Rd and having power, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, and has the display optical system being designed to direct the light from the display means to an observer by the use of the second optical element and presenting the enlarged image of an image on the display means, one of the eccentric reflecting surfaces of the first optical element and one of the eccentric reflecting surfaces of the second optical element using the front and back surfaces of the same shape of an optical path separating surface, the optical path separating surface being a half-transmitting reflecting surface, and being caused to function as a see-through optical system for causing light from the external world to be incident from the incidence surface of the first optical element, be transmitted through the optical path separating surface, to be emerged from the emergence surface of the second optical element and to be directed to an observer, and when a see-through reference ray passing through the center of the external world and the center of the exit pupil of the see-through optical system is defined as Rs, the display reference ray Rd and the see-through reference ray Rs may substantially coincide with the optical axis of the eyeball, and each of the see-through reference ray and the reference ray Ri of the image pickup optical system may substantially coincide with the optical axis of the external world.
Also, a compound display apparatus of this invention has an image pickup optical system satisfies
|fyp/fypout| less than 2
|fxp/fxpout| less than 2,
an image pickup element, display means and a second optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a display reference ray Rd and having power, wherein a beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold an optical path and is caused to emerge from the emergence surface, and has the display optical system being designed to direct the light from the display means to an observer by the use of the second optical element and passed the enlarged image of an image on the display means, one of the eccentric reflecting surface of the first optical element and one of the eccentric reflecting surfaces of the second optical element using the front and back surfaces of the same shape of an optical path separating surface, the optical path separating surfaces being a half-transmitting reflecting surface, and being caused to function as a see-through optical system for causing light from the external world to be incident from the incidence surface of the first optical element, be transmitted through the optical path separating surface, to be emerged from the emergence surface of the second optical element and to be directed to an observer, and when a see-through reference ray passing through the center of the external world and the center of the exit pupil of the see-through optical system is defined as Rs, the display reference ray Rd and the see-through reference ray Rs may substantially coincide with the optical axis of the eyeball, and each of the see-through reference ray and the reference ray Ri of the image pickup optical system may substantially coincide with the optical axis of the external world.
Also, in the above-described compound display apparatus, design may be made such that when the distance from the position of the evolved entrance pupil when the entrance pupil of the image pickup optical system is evolved on the visual axis to the position of the exit pupil of the display optical system is defined as Dpp and the distance from the emergence surface of the display optical system to the exit pupil of the display optical system is defined as er.
0.25 less than Dpp/er less than 8.0xe2x80x83xe2x80x83(7)
is satisfied.
Also, to solve the above-noted problems, the compound display apparatus of the present invention has a display optical system for directing a beam from display means displaying image information thereon to an observer""s eyeball, and an image pickup optical system for imaging a beam from the external world on an image pickup element, wherein the eyeball optical axis of the beam incident on the observer""s eyeball of the display optical system or a virtual eyeball optical axis extended from the eyeball optical axis and the external world optical axis of a beam incident from the external world of the image pickup optical system are made substantially coincident with each other by optical path separating means provided in the optical path, and is characterized in that the image pickup optical system has a first optical element having on the same medium an incidence surface, an emergence surface and a plurality of eccentric reflecting surfaces eccentric relative to a reference ray Ri and having power, at least one of the plurality of eccentric reflecting surfaces being a dual purpose surface used as a transmitting surface and reflecting surface in one, wherein the beam incident from the incidence surface is reflected by the plurality of eccentric reflecting surfaces to thereby fold the optical path and is caused to emerge from the emergence surface, and meridional section composite power is negative.
In the above-described compound display apparatus, the image pickup optical system may have a compound lens unit having at least one rotation-asymmetrical lens of which the opposite surfaces comprise a rotation-asymmetrical surface and a rotation-symmetrical surface, respectively, and a plurality of rotation-symmetrical lenses, wherein all of the optical axis of the rotation-symmetrical surface of the rotation-asymmetrical lens and the optical axes of the rotation-symmetrical lenses are substantially coincident with one another, and the beam from the external world may be passed through the first optical element, and thereafter be directed onto the image pickup element by the compound lens unit.
Also, in the above-described compound display apparatus, design may be made such that the local meridional section focal length fypout and local sagittal section focal length fxpout of the emergence surface of the first optical element and the meridional section composite focal length fyp and sagittal section composite focal length fxp of the optical element satisfy
|fyp/fypout| less than 2xe2x80x83xe2x80x83(1)
|fxp/fxpout| less than 2.xe2x80x83xe2x80x83(2)
Also, in the above-described compound display apparatus, design may be made such that the local meridional section focal length fyl and local sagittal section focal length fxl of the rotation-asymmetrical surface of the compound lens unit and the meridional section composite focal length fyg and sagittal section composite focal length fxg of the compound lens unit satisfy
|fyg/fyl| less than 1xe2x80x83xe2x80x83(3)
|fxg/fxl| less than 1.xe2x80x83xe2x80x83(4)
Also, in the above-described compound display apparatus, design may be made such that when the meridional section composite focal length of the entire image pickup optical system is defined as fy and the sagittal section composite focal length thereof is defined as fx and the meridional section composite focal length of the first optical element is defined as fyp and the sagittal section composite focal length thereof is defined as fxp,
xe2x88x921 less than fy/fyp less than 0xe2x80x83xe2x80x83(5)
xe2x88x921 less than fx/fxp less than 0xe2x80x83xe2x80x83(6)
are satisfied.
Also, in the above-described compound display apparatus, design may be made such that when the distance from the position of the evolved entrance pupil when the entrance pupil of the image pickup optical system is evolved on the visual axis to the position of the exit pupil of the display optical system is defined as Dpp and the distance from the emergence surface of the display optical system to the exit pupil of the display optical system is defined as er,
0.25 less than Dpp/er less than 8.0xe2x80x83xe2x80x83(7)
is satisfied.